I also do not know how long the bitcoin can last, but I'm sure bitcoin will last for a long time. I'm sure bitcoin will last forever.
But bitcoin can also become useless if the internet network in the world no longer exists or the internet network is damaged, and if the bit oin enthusiasts are no longer there, but you do not need to be wondering if bitcoin will no longer exist no other Crypto currency will appears after bitcoin.
Well, I will say that Bitcoin is also the foundation of the cryptocurrencies inside Internet and Cyber world. Internet and Internet connection makes the Bitcoin famous and popular. If it is gone already, Bitcoin become useless. But, I know that it will not gone because The new technologies will arise and all people wanted to have a good and reliable internet connection in the near future.